Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to rotary combustion engines and more specifically radial or rotary vane combustion engines that achieve sequential and simultaneous combustion.
2. Background of the Invention
Rotary engines have been recognized as having advantages over reciprocating engines by their superior inertial economy of fewer parts moving in a more concentric pattern about the torque axis. Most rotary designs dispose of parts that contribute to engine load and friction such as valves drive components and large components associated with translating torque to the crankshaft. The inherent simplicity of rotary engines contributes to a much smoother operation and the ability to achieve higher operating frequencies than reciprocating engines. Another great advantage of rotary engines is the ability to accomplish multiple sequential cycles in one revolution as opposed to Otto or Diesel cycles, which require the wasteful dynamics of an extra revolution to evacuate exhaust. These advantages cumulatively increase the volume of processed combustibles in a rotary engine relative to their displacement and proportionally increase their power to weight ratio. However, rotary and radial vane engines have several deficiencies related to the division of cycle processes performed by rotor apex or radial vane seals. These sealing components are exposed to high surface velocities and the extreme heat of rapid combustion concentrated in a relatively small thermal core. Another disadvantage of rotary engines is the relatively small mixing region used for creating a stoichiometric ratio before ignition. This is further complicated by the extremely short interval that combustibles must ignite in a region of varying geometry then expelled into an exhaust cycle incompletely burned.
This invention retains the above stated advantages of rotary and radial vane rotary engines but eliminates those problematic features mentioned. It accomplishes this by the application of expansion chambers that totally encase variable vanes within the rotor body. This configuration uniquely performs the power and compression cycle simultaneously by using the variable vane as a barrier between the working fluid and the inlet air. The inlet air, which is introduced through rotatably aligned rotor and housing inlets, floods the expansion chambers during the intake-exhaust cycle process. Air that enters the forward region of the expansion chamber is trapped by the vane, then compressed during the power-compression cycle and combined with fuel in a combustor of a sequential cycle.
The first notable distinction of this invention from most prior art is that stator inner walls are concentric, not radially asymmetric, and the rotor revolves concentrically about the main axis. This invention abandons the use of elliptical or asymmetrical chambers to facilitate compression through positive displacement between the rotor and stator as described in prior art by Pangman (U.S. Pat. No. 5,277,158), Penn (U.S. Pat. No. 5,540,199), and Tang (U.S. Pat. No. 6,125,814). These methods require vanes to move radially outward and retract into the rotor in order to seal the varying void between the stator and rotor and divide each cycle process. This invention also departs from such methods without the need of stator mechanics that seal to fixed radial vanes and divide the cycle processes such as those employed by Vanmoor (U.S. Pat. No. 6,003,486).
In contrast, the variable vanes in this invention never come in contact or have to seal to the stator inner walls, as they are totally encased within interior expansion chambers. Sealing tolerances are not as critical as is in other rotary engines because combustive gases that breach the variable vane periphery do not greatly effect the compression of the chamber. Quite uniquely, they contribute to the compression region pressure until the two voids reach equilibrium. It is also important to note that the power-compression cycle occurs in such a short interval, only negligible combustive gases achieve this breach and subsequent combustion of the compressed air is not affected.
As stated above, many problems are associated with cooling and thermodynamic losses in rotary engine designs. The cooling problems are associated with the fact that most rotary engine designs take advantage of superior balancing and achieve higher operating frequencies while performing multiple cycles per rotation. Because of the relatively small thermal core of a rotary engine relative to the power produced, the need to remove excess heat is essential to the preservation of the internal parts. In the prescribed method of this invention, inlet air moves freely into the thermal core of the rotor via rotatably aligned housing inlets. A large percentage of the air passes through the expansion chamber and facilitates rotor cooling while expelling exhaust gas. The remainder of the air is trapped by the variable vane in the forward compression region of the expansion chamber where it is compressed and discharged through diffuser ports that recycle heat back into the combustor. This method has the dual advantage of providing inner cooling while reclaiming some of the thermodynamic losses in a regenerative cycle.
As stated above, this invention employs isolated combustion regions or combustors to achieve concise stoichiometric control in a constant geometric cross-section. This has many advantages over other rotary engines that mix combustibles in smaller, constantly changing geometric combustion regions that contribute to unburned or xe2x80x9cwettedxe2x80x9d fuel. Another major advantage is that combustors are able to maintain a continuous flame front without the need for ignition timing. Combustors also have multi-fuel compatibility and allow for thermodynamic quenching before the primary combustion region temperatures are exposed to the internal rotor parts. This is an important feature in light of developments in plasma ignition systems that use extreme temperatures to completely burn reluctant or lean mixtures and reduce emissions.
A combustor utilizing a plasma ignition source is perfectly suited for this invention because the internal components are thermally isolated from the extreme temperatures in the combustor.
It is the object of this invention to provide a rotary engine that is compact, lightweight, and simple to manufacture.
It is an additional object of this invention to provide a rotary engine that achieves improved efficiency and increased fuel economy.
It is also the object of this invention to provide a rotary engine with improved combustion yielding significantly lower emissions.
It is yet another object of this invention to provide a rotary engine that can use a variety of fuels.
In accordance with these objectives, this invention provides a variable vane rotary engine comprising of a concentric housing formed by a stator with front and rear covers enclosing an inner space. Disposed within this inner space is a rotor rotatably mounted on a central axis spaced within close tolerance of the stator inner wall. Inside the rotor are symmetrically positioned expansion chambers each containing a variable vane articulated on a pivot axis. The shape of the expansion chambers voids can best be described as xe2x80x9ccheese wedgesxe2x80x9d with round peripheral edges. The expansion chambers and vanes are exposed to the stator wall via peripheral rotor combustion ducts that enter the rotationally rearward inner wall of each chamber. Positioned at the beginning of each power-compression cycle process section of the stator are combustion ports coupled to a combustor via nozzle. Positioned throughout each intake-exhaust cycle process section of the stator are exhaust ducts.
Torque is produced when the combustors discharge their working fluid into the expansion chamber providing rotational energy to the rotor. The variable vanes, precisely controlled as the cycle progresses, simultaneously compress air brought in during the intake-exhaust cycle process and force this compressed air through rotationally aligned diffuser ports. The compressed air is then routed through a compression plenum to compliment the combustion for a combustor of a sequential cycle. The efficiency of this invention is attributed to the small number of moving parts and their respectively low frictional forces. Additionally, all moving parts rotate about the main shaft axis and contribute to a common moment of torque.
Many combinations of expansion chambers and combustors can be applied to acquire the desired output. This invention can also be constructed with one rotor or a multiple of rotors coupled to the same output shaft. Examples in the embodiment depict a single rotor configuration containing five expansion chambers and two external combustors yielding ten full cycles per revolution. A full cycle is considered to be both the power-compression cycle process and the intake-exhaust cycle process. The total number of cycles per revolution is a multiple of the expansion chambers and the number of combustors.